738065f765abd4dda88a9f762736f9a1108cb6fd
[sfrench/cifs-2.6.git] / mm / huge_memory.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  Copyright (C) 2009  Red Hat, Inc.
4  */
5
6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7
8 #include <linux/mm.h>
9 #include <linux/sched.h>
10 #include <linux/sched/coredump.h>
11 #include <linux/sched/numa_balancing.h>
12 #include <linux/highmem.h>
13 #include <linux/hugetlb.h>
14 #include <linux/mmu_notifier.h>
15 #include <linux/rmap.h>
16 #include <linux/swap.h>
17 #include <linux/shrinker.h>
18 #include <linux/mm_inline.h>
19 #include <linux/swapops.h>
20 #include <linux/dax.h>
21 #include <linux/khugepaged.h>
22 #include <linux/freezer.h>
23 #include <linux/pfn_t.h>
24 #include <linux/mman.h>
25 #include <linux/memremap.h>
26 #include <linux/pagemap.h>
27 #include <linux/debugfs.h>
28 #include <linux/migrate.h>
29 #include <linux/hashtable.h>
30 #include <linux/userfaultfd_k.h>
31 #include <linux/page_idle.h>
32 #include <linux/shmem_fs.h>
33 #include <linux/oom.h>
34 #include <linux/numa.h>
35
36 #include <asm/tlb.h>
37 #include <asm/pgalloc.h>
38 #include "internal.h"
39
40 /*
41  * By default, transparent hugepage support is disabled in order to avoid
42  * risking an increased memory footprint for applications that are not
43  * guaranteed to benefit from it. When transparent hugepage support is
44  * enabled, it is for all mappings, and khugepaged scans all mappings.
45  * Defrag is invoked by khugepaged hugepage allocations and by page faults
46  * for all hugepage allocations.
47  */
48 unsigned long transparent_hugepage_flags __read_mostly =
49 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
50         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
51 #endif
52 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
53         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
54 #endif
55         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
56         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
57         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
58
59 static struct shrinker deferred_split_shrinker;
60
61 static atomic_t huge_zero_refcount;
62 struct page *huge_zero_page __read_mostly;
63
64 bool transparent_hugepage_enabled(struct vm_area_struct *vma)
65 {
66         /* The addr is used to check if the vma size fits */
67         unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE;
68
69         if (!transhuge_vma_suitable(vma, addr))
70                 return false;
71         if (vma_is_anonymous(vma))
72                 return __transparent_hugepage_enabled(vma);
73         if (vma_is_shmem(vma))
74                 return shmem_huge_enabled(vma);
75
76         return false;
77 }
78
79 static struct page *get_huge_zero_page(void)
80 {
81         struct page *zero_page;
82 retry:
83         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
84                 return READ_ONCE(huge_zero_page);
85
86         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
87                         HPAGE_PMD_ORDER);
88         if (!zero_page) {
89                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
90                 return NULL;
91         }
92         count_vm_event(THP_ZERO_PAGE_ALLOC);
93         preempt_disable();
94         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
95                 preempt_enable();
96                 __free_pages(zero_page, compound_order(zero_page));
97                 goto retry;
98         }
99
100         /* We take additional reference here. It will be put back by shrinker */
101         atomic_set(&huge_zero_refcount, 2);
102         preempt_enable();
103         return READ_ONCE(huge_zero_page);
104 }
105
106 static void put_huge_zero_page(void)
107 {
108         /*
109          * Counter should never go to zero here. Only shrinker can put
110          * last reference.
111          */
112         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
113 }
114
115 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
116 {
117         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
118                 return READ_ONCE(huge_zero_page);
119
120         if (!get_huge_zero_page())
121                 return NULL;
122
123         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
124                 put_huge_zero_page();
125
126         return READ_ONCE(huge_zero_page);
127 }
128
129 void mm_put_huge_zero_page(struct mm_struct *mm)
130 {
131         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
132                 put_huge_zero_page();
133 }
134
135 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
136                                         struct shrink_control *sc)
137 {
138         /* we can free zero page only if last reference remains */
139         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
140 }
141
142 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
143                                        struct shrink_control *sc)
144 {
145         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
146                 struct page *zero_page = xchg(&huge_zero_page, NULL);
147                 BUG_ON(zero_page == NULL);
148                 __free_pages(zero_page, compound_order(zero_page));
149                 return HPAGE_PMD_NR;
150         }
151
152         return 0;
153 }
154
155 static struct shrinker huge_zero_page_shrinker = {
156         .count_objects = shrink_huge_zero_page_count,
157         .scan_objects = shrink_huge_zero_page_scan,
158         .seeks = DEFAULT_SEEKS,
159 };
160
161 #ifdef CONFIG_SYSFS
162 static ssize_t enabled_show(struct kobject *kobj,
163                             struct kobj_attribute *attr, char *buf)
164 {
165         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
166                 return sprintf(buf, "[always] madvise never\n");
167         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
168                 return sprintf(buf, "always [madvise] never\n");
169         else
170                 return sprintf(buf, "always madvise [never]\n");
171 }
172
173 static ssize_t enabled_store(struct kobject *kobj,
174                              struct kobj_attribute *attr,
175                              const char *buf, size_t count)
176 {
177         ssize_t ret = count;
178
179         if (!memcmp("always", buf,
180                     min(sizeof("always")-1, count))) {
181                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
182                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
183         } else if (!memcmp("madvise", buf,
184                            min(sizeof("madvise")-1, count))) {
185                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
186                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
187         } else if (!memcmp("never", buf,
188                            min(sizeof("never")-1, count))) {
189                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
190                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
191         } else
192                 ret = -EINVAL;
193
194         if (ret > 0) {
195                 int err = start_stop_khugepaged();
196                 if (err)
197                         ret = err;
198         }
199         return ret;
200 }
201 static struct kobj_attribute enabled_attr =
202         __ATTR(enabled, 0644, enabled_show, enabled_store);
203
204 ssize_t single_hugepage_flag_show(struct kobject *kobj,
205                                 struct kobj_attribute *attr, char *buf,
206                                 enum transparent_hugepage_flag flag)
207 {
208         return sprintf(buf, "%d\n",
209                        !!test_bit(flag, &transparent_hugepage_flags));
210 }
211
212 ssize_t single_hugepage_flag_store(struct kobject *kobj,
213                                  struct kobj_attribute *attr,
214                                  const char *buf, size_t count,
215                                  enum transparent_hugepage_flag flag)
216 {
217         unsigned long value;
218         int ret;
219
220         ret = kstrtoul(buf, 10, &value);
221         if (ret < 0)
222                 return ret;
223         if (value > 1)
224                 return -EINVAL;
225
226         if (value)
227                 set_bit(flag, &transparent_hugepage_flags);
228         else
229                 clear_bit(flag, &transparent_hugepage_flags);
230
231         return count;
232 }
233
234 static ssize_t defrag_show(struct kobject *kobj,
235                            struct kobj_attribute *attr, char *buf)
236 {
237         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
238                 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
239         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
240                 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
241         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
242                 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
243         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
244                 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
245         return sprintf(buf, "always defer defer+madvise madvise [never]\n");
246 }
247
248 static ssize_t defrag_store(struct kobject *kobj,
249                             struct kobj_attribute *attr,
250                             const char *buf, size_t count)
251 {
252         if (!memcmp("always", buf,
253                     min(sizeof("always")-1, count))) {
254                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
255                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
256                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
257                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
258         } else if (!memcmp("defer+madvise", buf,
259                     min(sizeof("defer+madvise")-1, count))) {
260                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
261                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
262                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
263                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
264         } else if (!memcmp("defer", buf,
265                     min(sizeof("defer")-1, count))) {
266                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
267                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
268                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
269                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
270         } else if (!memcmp("madvise", buf,
271                            min(sizeof("madvise")-1, count))) {
272                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
273                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
274                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
275                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
276         } else if (!memcmp("never", buf,
277                            min(sizeof("never")-1, count))) {
278                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
279                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
280                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
281                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
282         } else
283                 return -EINVAL;
284
285         return count;
286 }
287 static struct kobj_attribute defrag_attr =
288         __ATTR(defrag, 0644, defrag_show, defrag_store);
289
290 static ssize_t use_zero_page_show(struct kobject *kobj,
291                 struct kobj_attribute *attr, char *buf)
292 {
293         return single_hugepage_flag_show(kobj, attr, buf,
294                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
295 }
296 static ssize_t use_zero_page_store(struct kobject *kobj,
297                 struct kobj_attribute *attr, const char *buf, size_t count)
298 {
299         return single_hugepage_flag_store(kobj, attr, buf, count,
300                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
301 }
302 static struct kobj_attribute use_zero_page_attr =
303         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
304
305 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
306                 struct kobj_attribute *attr, char *buf)
307 {
308         return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
309 }
310 static struct kobj_attribute hpage_pmd_size_attr =
311         __ATTR_RO(hpage_pmd_size);
312
313 #ifdef CONFIG_DEBUG_VM
314 static ssize_t debug_cow_show(struct kobject *kobj,
315                                 struct kobj_attribute *attr, char *buf)
316 {
317         return single_hugepage_flag_show(kobj, attr, buf,
318                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
319 }
320 static ssize_t debug_cow_store(struct kobject *kobj,
321                                struct kobj_attribute *attr,
322                                const char *buf, size_t count)
323 {
324         return single_hugepage_flag_store(kobj, attr, buf, count,
325                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
326 }
327 static struct kobj_attribute debug_cow_attr =
328         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
329 #endif /* CONFIG_DEBUG_VM */
330
331 static struct attribute *hugepage_attr[] = {
332         &enabled_attr.attr,
333         &defrag_attr.attr,
334         &use_zero_page_attr.attr,
335         &hpage_pmd_size_attr.attr,
336 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
337         &shmem_enabled_attr.attr,
338 #endif
339 #ifdef CONFIG_DEBUG_VM
340         &debug_cow_attr.attr,
341 #endif
342         NULL,
343 };
344
345 static const struct attribute_group hugepage_attr_group = {
346         .attrs = hugepage_attr,
347 };
348
349 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
350 {
351         int err;
352
353         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
354         if (unlikely(!*hugepage_kobj)) {
355                 pr_err("failed to create transparent hugepage kobject\n");
356                 return -ENOMEM;
357         }
358
359         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
360         if (err) {
361                 pr_err("failed to register transparent hugepage group\n");
362                 goto delete_obj;
363         }
364
365         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
366         if (err) {
367                 pr_err("failed to register transparent hugepage group\n");
368                 goto remove_hp_group;
369         }
370
371         return 0;
372
373 remove_hp_group:
374         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
375 delete_obj:
376         kobject_put(*hugepage_kobj);
377         return err;
378 }
379
380 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
381 {
382         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
383         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
384         kobject_put(hugepage_kobj);
385 }
386 #else
387 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
388 {
389         return 0;
390 }
391
392 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
393 {
394 }
395 #endif /* CONFIG_SYSFS */
396
397 static int __init hugepage_init(void)
398 {
399         int err;
400         struct kobject *hugepage_kobj;
401
402         if (!has_transparent_hugepage()) {
403                 transparent_hugepage_flags = 0;
404                 return -EINVAL;
405         }
406
407         /*
408          * hugepages can't be allocated by the buddy allocator
409          */
410         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
411         /*
412          * we use page->mapping and page->index in second tail page
413          * as list_head: assuming THP order >= 2
414          */
415         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
416
417         err = hugepage_init_sysfs(&hugepage_kobj);
418         if (err)
419                 goto err_sysfs;
420
421         err = khugepaged_init();
422         if (err)
423                 goto err_slab;
424
425         err = register_shrinker(&huge_zero_page_shrinker);
426         if (err)
427                 goto err_hzp_shrinker;
428         err = register_shrinker(&deferred_split_shrinker);
429         if (err)
430                 goto err_split_shrinker;
431
432         /*
433          * By default disable transparent hugepages on smaller systems,
434          * where the extra memory used could hurt more than TLB overhead
435          * is likely to save.  The admin can still enable it through /sys.
436          */
437         if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
438                 transparent_hugepage_flags = 0;
439                 return 0;
440         }
441
442         err = start_stop_khugepaged();
443         if (err)
444                 goto err_khugepaged;
445
446         return 0;
447 err_khugepaged:
448         unregister_shrinker(&deferred_split_shrinker);
449 err_split_shrinker:
450         unregister_shrinker(&huge_zero_page_shrinker);
451 err_hzp_shrinker:
452         khugepaged_destroy();
453 err_slab:
454         hugepage_exit_sysfs(hugepage_kobj);
455 err_sysfs:
456         return err;
457 }
458 subsys_initcall(hugepage_init);
459
460 static int __init setup_transparent_hugepage(char *str)
461 {
462         int ret = 0;
463         if (!str)
464                 goto out;
465         if (!strcmp(str, "always")) {
466                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
467                         &transparent_hugepage_flags);
468                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
469                           &transparent_hugepage_flags);
470                 ret = 1;
471         } else if (!strcmp(str, "madvise")) {
472                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
473                           &transparent_hugepage_flags);
474                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
475                         &transparent_hugepage_flags);
476                 ret = 1;
477         } else if (!strcmp(str, "never")) {
478                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
479                           &transparent_hugepage_flags);
480                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
481                           &transparent_hugepage_flags);
482                 ret = 1;
483         }
484 out:
485         if (!ret)
486                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
487         return ret;
488 }
489 __setup("transparent_hugepage=", setup_transparent_hugepage);
490
491 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
492 {
493         if (likely(vma->vm_flags & VM_WRITE))
494                 pmd = pmd_mkwrite(pmd);
495         return pmd;
496 }
497
498 static inline struct list_head *page_deferred_list(struct page *page)
499 {
500         /* ->lru in the tail pages is occupied by compound_head. */
501         return &page[2].deferred_list;
502 }
503
504 void prep_transhuge_page(struct page *page)
505 {
506         /*
507          * we use page->mapping and page->indexlru in second tail page
508          * as list_head: assuming THP order >= 2
509          */
510
511         INIT_LIST_HEAD(page_deferred_list(page));
512         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
513 }
514
515 static unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
516                 loff_t off, unsigned long flags, unsigned long size)
517 {
518         unsigned long addr;
519         loff_t off_end = off + len;
520         loff_t off_align = round_up(off, size);
521         unsigned long len_pad;
522
523         if (off_end <= off_align || (off_end - off_align) < size)
524                 return 0;
525
526         len_pad = len + size;
527         if (len_pad < len || (off + len_pad) < off)
528                 return 0;
529
530         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
531                                               off >> PAGE_SHIFT, flags);
532         if (IS_ERR_VALUE(addr))
533                 return 0;
534
535         addr += (off - addr) & (size - 1);
536         return addr;
537 }
538
539 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
540                 unsigned long len, unsigned long pgoff, unsigned long flags)
541 {
542         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
543
544         if (addr)
545                 goto out;
546         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
547                 goto out;
548
549         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
550         if (addr)
551                 return addr;
552
553  out:
554         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
555 }
556 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
557
558 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
559                         struct page *page, gfp_t gfp)
560 {
561         struct vm_area_struct *vma = vmf->vma;
562         struct mem_cgroup *memcg;
563         pgtable_t pgtable;
564         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
565         vm_fault_t ret = 0;
566
567         VM_BUG_ON_PAGE(!PageCompound(page), page);
568
569         if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
570                 put_page(page);
571                 count_vm_event(THP_FAULT_FALLBACK);
572                 return VM_FAULT_FALLBACK;
573         }
574
575         pgtable = pte_alloc_one(vma->vm_mm);
576         if (unlikely(!pgtable)) {
577                 ret = VM_FAULT_OOM;
578                 goto release;
579         }
580
581         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
582         /*
583          * The memory barrier inside __SetPageUptodate makes sure that
584          * clear_huge_page writes become visible before the set_pmd_at()
585          * write.
586          */
587         __SetPageUptodate(page);
588
589         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
590         if (unlikely(!pmd_none(*vmf->pmd))) {
591                 goto unlock_release;
592         } else {
593                 pmd_t entry;
594
595                 ret = check_stable_address_space(vma->vm_mm);
596                 if (ret)
597                         goto unlock_release;
598
599                 /* Deliver the page fault to userland */
600                 if (userfaultfd_missing(vma)) {
601                         vm_fault_t ret2;
602
603                         spin_unlock(vmf->ptl);
604                         mem_cgroup_cancel_charge(page, memcg, true);
605                         put_page(page);
606                         pte_free(vma->vm_mm, pgtable);
607                         ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
608                         VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
609                         return ret2;
610                 }
611
612                 entry = mk_huge_pmd(page, vma->vm_page_prot);
613                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
614                 page_add_new_anon_rmap(page, vma, haddr, true);
615                 mem_cgroup_commit_charge(page, memcg, false, true);
616                 lru_cache_add_active_or_unevictable(page, vma);
617                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
618                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
619                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
620                 mm_inc_nr_ptes(vma->vm_mm);
621                 spin_unlock(vmf->ptl);
622                 count_vm_event(THP_FAULT_ALLOC);
623                 count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
624         }
625
626         return 0;
627 unlock_release:
628         spin_unlock(vmf->ptl);
629 release:
630         if (pgtable)
631                 pte_free(vma->vm_mm, pgtable);
632         mem_cgroup_cancel_charge(page, memcg, true);
633         put_page(page);
634         return ret;
635
636 }
637
638 /*
639  * always: directly stall for all thp allocations
640  * defer: wake kswapd and fail if not immediately available
641  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
642  *                fail if not immediately available
643  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
644  *          available
645  * never: never stall for any thp allocation
646  */
647 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma, unsigned long addr)
648 {
649         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
650         gfp_t this_node = 0;
651
652 #ifdef CONFIG_NUMA
653         struct mempolicy *pol;
654         /*
655          * __GFP_THISNODE is used only when __GFP_DIRECT_RECLAIM is not
656          * specified, to express a general desire to stay on the current
657          * node for optimistic allocation attempts. If the defrag mode
658          * and/or madvise hint requires the direct reclaim then we prefer
659          * to fallback to other node rather than node reclaim because that
660          * can lead to excessive reclaim even though there is free memory
661          * on other nodes. We expect that NUMA preferences are specified
662          * by memory policies.
663          */
664         pol = get_vma_policy(vma, addr);
665         if (pol->mode != MPOL_BIND)
666                 this_node = __GFP_THISNODE;
667         mpol_cond_put(pol);
668 #endif
669
670         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
671                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
672         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
673                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM | this_node;
674         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
675                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
676                                                              __GFP_KSWAPD_RECLAIM | this_node);
677         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
678                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
679                                                              this_node);
680         return GFP_TRANSHUGE_LIGHT | this_node;
681 }
682
683 /* Caller must hold page table lock. */
684 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
685                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
686                 struct page *zero_page)
687 {
688         pmd_t entry;
689         if (!pmd_none(*pmd))
690                 return false;
691         entry = mk_pmd(zero_page, vma->vm_page_prot);
692         entry = pmd_mkhuge(entry);
693         if (pgtable)
694                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
695         set_pmd_at(mm, haddr, pmd, entry);
696         mm_inc_nr_ptes(mm);
697         return true;
698 }
699
700 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
701 {
702         struct vm_area_struct *vma = vmf->vma;
703         gfp_t gfp;
704         struct page *page;
705         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
706
707         if (!transhuge_vma_suitable(vma, haddr))
708                 return VM_FAULT_FALLBACK;
709         if (unlikely(anon_vma_prepare(vma)))
710                 return VM_FAULT_OOM;
711         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
712                 return VM_FAULT_OOM;
713         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
714                         !mm_forbids_zeropage(vma->vm_mm) &&
715                         transparent_hugepage_use_zero_page()) {
716                 pgtable_t pgtable;
717                 struct page *zero_page;
718                 bool set;
719                 vm_fault_t ret;
720                 pgtable = pte_alloc_one(vma->vm_mm);
721                 if (unlikely(!pgtable))
722                         return VM_FAULT_OOM;
723                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
724                 if (unlikely(!zero_page)) {
725                         pte_free(vma->vm_mm, pgtable);
726                         count_vm_event(THP_FAULT_FALLBACK);
727                         return VM_FAULT_FALLBACK;
728                 }
729                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
730                 ret = 0;
731                 set = false;
732                 if (pmd_none(*vmf->pmd)) {
733                         ret = check_stable_address_space(vma->vm_mm);
734                         if (ret) {
735                                 spin_unlock(vmf->ptl);
736                         } else if (userfaultfd_missing(vma)) {
737                                 spin_unlock(vmf->ptl);
738                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
739                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
740                         } else {
741                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
742                                                    haddr, vmf->pmd, zero_page);
743                                 spin_unlock(vmf->ptl);
744                                 set = true;
745                         }
746                 } else
747                         spin_unlock(vmf->ptl);
748                 if (!set)
749                         pte_free(vma->vm_mm, pgtable);
750                 return ret;
751         }
752         gfp = alloc_hugepage_direct_gfpmask(vma, haddr);
753         page = alloc_pages_vma(gfp, HPAGE_PMD_ORDER, vma, haddr, numa_node_id());
754         if (unlikely(!page)) {
755                 count_vm_event(THP_FAULT_FALLBACK);
756                 return VM_FAULT_FALLBACK;
757         }
758         prep_transhuge_page(page);
759         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
760 }
761
762 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
763                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
764                 pgtable_t pgtable)
765 {
766         struct mm_struct *mm = vma->vm_mm;
767         pmd_t entry;
768         spinlock_t *ptl;
769
770         ptl = pmd_lock(mm, pmd);
771         if (!pmd_none(*pmd)) {
772                 if (write) {
773                         if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
774                                 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
775                                 goto out_unlock;
776                         }
777                         entry = pmd_mkyoung(*pmd);
778                         entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
779                         if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
780                                 update_mmu_cache_pmd(vma, addr, pmd);
781                 }
782
783                 goto out_unlock;
784         }
785
786         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
787         if (pfn_t_devmap(pfn))
788                 entry = pmd_mkdevmap(entry);
789         if (write) {
790                 entry = pmd_mkyoung(pmd_mkdirty(entry));
791                 entry = maybe_pmd_mkwrite(entry, vma);
792         }
793
794         if (pgtable) {
795                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
796                 mm_inc_nr_ptes(mm);
797                 pgtable = NULL;
798         }
799
800         set_pmd_at(mm, addr, pmd, entry);
801         update_mmu_cache_pmd(vma, addr, pmd);
802
803 out_unlock:
804         spin_unlock(ptl);
805         if (pgtable)
806                 pte_free(mm, pgtable);
807 }
808
809 vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write)
810 {
811         unsigned long addr = vmf->address & PMD_MASK;
812         struct vm_area_struct *vma = vmf->vma;
813         pgprot_t pgprot = vma->vm_page_prot;
814         pgtable_t pgtable = NULL;
815
816         /*
817          * If we had pmd_special, we could avoid all these restrictions,
818          * but we need to be consistent with PTEs and architectures that
819          * can't support a 'special' bit.
820          */
821         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
822                         !pfn_t_devmap(pfn));
823         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
824                                                 (VM_PFNMAP|VM_MIXEDMAP));
825         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
826
827         if (addr < vma->vm_start || addr >= vma->vm_end)
828                 return VM_FAULT_SIGBUS;
829
830         if (arch_needs_pgtable_deposit()) {
831                 pgtable = pte_alloc_one(vma->vm_mm);
832                 if (!pgtable)
833                         return VM_FAULT_OOM;
834         }
835
836         track_pfn_insert(vma, &pgprot, pfn);
837
838         insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
839         return VM_FAULT_NOPAGE;
840 }
841 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
842
843 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
844 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
845 {
846         if (likely(vma->vm_flags & VM_WRITE))
847                 pud = pud_mkwrite(pud);
848         return pud;
849 }
850
851 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
852                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
853 {
854         struct mm_struct *mm = vma->vm_mm;
855         pud_t entry;
856         spinlock_t *ptl;
857
858         ptl = pud_lock(mm, pud);
859         if (!pud_none(*pud)) {
860                 if (write) {
861                         if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
862                                 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
863                                 goto out_unlock;
864                         }
865                         entry = pud_mkyoung(*pud);
866                         entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
867                         if (pudp_set_access_flags(vma, addr, pud, entry, 1))
868                                 update_mmu_cache_pud(vma, addr, pud);
869                 }
870                 goto out_unlock;
871         }
872
873         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
874         if (pfn_t_devmap(pfn))
875                 entry = pud_mkdevmap(entry);
876         if (write) {
877                 entry = pud_mkyoung(pud_mkdirty(entry));
878                 entry = maybe_pud_mkwrite(entry, vma);
879         }
880         set_pud_at(mm, addr, pud, entry);
881         update_mmu_cache_pud(vma, addr, pud);
882
883 out_unlock:
884         spin_unlock(ptl);
885 }
886
887 vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
888 {
889         unsigned long addr = vmf->address & PUD_MASK;
890         struct vm_area_struct *vma = vmf->vma;
891         pgprot_t pgprot = vma->vm_page_prot;
892
893         /*
894          * If we had pud_special, we could avoid all these restrictions,
895          * but we need to be consistent with PTEs and architectures that
896          * can't support a 'special' bit.
897          */
898         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
899                         !pfn_t_devmap(pfn));
900         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
901                                                 (VM_PFNMAP|VM_MIXEDMAP));
902         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
903
904         if (addr < vma->vm_start || addr >= vma->vm_end)
905                 return VM_FAULT_SIGBUS;
906
907         track_pfn_insert(vma, &pgprot, pfn);
908
909         insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
910         return VM_FAULT_NOPAGE;
911 }
912 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
913 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
914
915 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
916                 pmd_t *pmd, int flags)
917 {
918         pmd_t _pmd;
919
920         _pmd = pmd_mkyoung(*pmd);
921         if (flags & FOLL_WRITE)
922                 _pmd = pmd_mkdirty(_pmd);
923         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
924                                 pmd, _pmd, flags & FOLL_WRITE))
925                 update_mmu_cache_pmd(vma, addr, pmd);
926 }
927
928 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
929                 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
930 {
931         unsigned long pfn = pmd_pfn(*pmd);
932         struct mm_struct *mm = vma->vm_mm;
933         struct page *page;
934
935         assert_spin_locked(pmd_lockptr(mm, pmd));
936
937         /*
938          * When we COW a devmap PMD entry, we split it into PTEs, so we should
939          * not be in this function with `flags & FOLL_COW` set.
940          */
941         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
942
943         if (flags & FOLL_WRITE && !pmd_write(*pmd))
944                 return NULL;
945
946         if (pmd_present(*pmd) && pmd_devmap(*pmd))
947                 /* pass */;
948         else
949                 return NULL;
950
951         if (flags & FOLL_TOUCH)
952                 touch_pmd(vma, addr, pmd, flags);
953
954         /*
955          * device mapped pages can only be returned if the
956          * caller will manage the page reference count.
957          */
958         if (!(flags & FOLL_GET))
959                 return ERR_PTR(-EEXIST);
960
961         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
962         *pgmap = get_dev_pagemap(pfn, *pgmap);
963         if (!*pgmap)
964                 return ERR_PTR(-EFAULT);
965         page = pfn_to_page(pfn);
966         get_page(page);
967
968         return page;
969 }
970
971 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
972                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
973                   struct vm_area_struct *vma)
974 {
975         spinlock_t *dst_ptl, *src_ptl;
976         struct page *src_page;
977         pmd_t pmd;
978         pgtable_t pgtable = NULL;
979         int ret = -ENOMEM;
980
981         /* Skip if can be re-fill on fault */
982         if (!vma_is_anonymous(vma))
983                 return 0;
984
985         pgtable = pte_alloc_one(dst_mm);
986         if (unlikely(!pgtable))
987                 goto out;
988
989         dst_ptl = pmd_lock(dst_mm, dst_pmd);
990         src_ptl = pmd_lockptr(src_mm, src_pmd);
991         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
992
993         ret = -EAGAIN;
994         pmd = *src_pmd;
995
996 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
997         if (unlikely(is_swap_pmd(pmd))) {
998                 swp_entry_t entry = pmd_to_swp_entry(pmd);
999
1000                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
1001                 if (is_write_migration_entry(entry)) {
1002                         make_migration_entry_read(&entry);
1003                         pmd = swp_entry_to_pmd(entry);
1004                         if (pmd_swp_soft_dirty(*src_pmd))
1005                                 pmd = pmd_swp_mksoft_dirty(pmd);
1006                         set_pmd_at(src_mm, addr, src_pmd, pmd);
1007                 }
1008                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1009                 mm_inc_nr_ptes(dst_mm);
1010                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1011                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1012                 ret = 0;
1013                 goto out_unlock;
1014         }
1015 #endif
1016
1017         if (unlikely(!pmd_trans_huge(pmd))) {
1018                 pte_free(dst_mm, pgtable);
1019                 goto out_unlock;
1020         }
1021         /*
1022          * When page table lock is held, the huge zero pmd should not be
1023          * under splitting since we don't split the page itself, only pmd to
1024          * a page table.
1025          */
1026         if (is_huge_zero_pmd(pmd)) {
1027                 struct page *zero_page;
1028                 /*
1029                  * get_huge_zero_page() will never allocate a new page here,
1030                  * since we already have a zero page to copy. It just takes a
1031                  * reference.
1032                  */
1033                 zero_page = mm_get_huge_zero_page(dst_mm);
1034                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1035                                 zero_page);
1036                 ret = 0;
1037                 goto out_unlock;
1038         }
1039
1040         src_page = pmd_page(pmd);
1041         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1042         get_page(src_page);
1043         page_dup_rmap(src_page, true);
1044         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1045         mm_inc_nr_ptes(dst_mm);
1046         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1047
1048         pmdp_set_wrprotect(src_mm, addr, src_pmd);
1049         pmd = pmd_mkold(pmd_wrprotect(pmd));
1050         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1051
1052         ret = 0;
1053 out_unlock:
1054         spin_unlock(src_ptl);
1055         spin_unlock(dst_ptl);
1056 out:
1057         return ret;
1058 }
1059
1060 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1061 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1062                 pud_t *pud, int flags)
1063 {
1064         pud_t _pud;
1065
1066         _pud = pud_mkyoung(*pud);
1067         if (flags & FOLL_WRITE)
1068                 _pud = pud_mkdirty(_pud);
1069         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1070                                 pud, _pud, flags & FOLL_WRITE))
1071                 update_mmu_cache_pud(vma, addr, pud);
1072 }
1073
1074 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1075                 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1076 {
1077         unsigned long pfn = pud_pfn(*pud);
1078         struct mm_struct *mm = vma->vm_mm;
1079         struct page *page;
1080
1081         assert_spin_locked(pud_lockptr(mm, pud));
1082
1083         if (flags & FOLL_WRITE && !pud_write(*pud))
1084                 return NULL;
1085
1086         if (pud_present(*pud) && pud_devmap(*pud))
1087                 /* pass */;
1088         else
1089                 return NULL;
1090
1091         if (flags & FOLL_TOUCH)
1092                 touch_pud(vma, addr, pud, flags);
1093
1094         /*
1095          * device mapped pages can only be returned if the
1096          * caller will manage the page reference count.
1097          */
1098         if (!(flags & FOLL_GET))
1099                 return ERR_PTR(-EEXIST);
1100
1101         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1102         *pgmap = get_dev_pagemap(pfn, *pgmap);
1103         if (!*pgmap)
1104                 return ERR_PTR(-EFAULT);
1105         page = pfn_to_page(pfn);
1106         get_page(page);
1107
1108         return page;
1109 }
1110
1111 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1112                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1113                   struct vm_area_struct *vma)
1114 {
1115         spinlock_t *dst_ptl, *src_ptl;
1116         pud_t pud;
1117         int ret;
1118
1119         dst_ptl = pud_lock(dst_mm, dst_pud);
1120         src_ptl = pud_lockptr(src_mm, src_pud);
1121         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1122
1123         ret = -EAGAIN;
1124         pud = *src_pud;
1125         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1126                 goto out_unlock;
1127
1128         /*
1129          * When page table lock is held, the huge zero pud should not be
1130          * under splitting since we don't split the page itself, only pud to
1131          * a page table.
1132          */
1133         if (is_huge_zero_pud(pud)) {
1134                 /* No huge zero pud yet */
1135         }
1136
1137         pudp_set_wrprotect(src_mm, addr, src_pud);
1138         pud = pud_mkold(pud_wrprotect(pud));
1139         set_pud_at(dst_mm, addr, dst_pud, pud);
1140
1141         ret = 0;
1142 out_unlock:
1143         spin_unlock(src_ptl);
1144         spin_unlock(dst_ptl);
1145         return ret;
1146 }
1147
1148 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1149 {
1150         pud_t entry;
1151         unsigned long haddr;
1152         bool write = vmf->flags & FAULT_FLAG_WRITE;
1153
1154         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1155         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1156                 goto unlock;
1157
1158         entry = pud_mkyoung(orig_pud);
1159         if (write)
1160                 entry = pud_mkdirty(entry);
1161         haddr = vmf->address & HPAGE_PUD_MASK;
1162         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1163                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1164
1165 unlock:
1166         spin_unlock(vmf->ptl);
1167 }
1168 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1169
1170 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1171 {
1172         pmd_t entry;
1173         unsigned long haddr;
1174         bool write = vmf->flags & FAULT_FLAG_WRITE;
1175
1176         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1177         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1178                 goto unlock;
1179
1180         entry = pmd_mkyoung(orig_pmd);
1181         if (write)
1182                 entry = pmd_mkdirty(entry);
1183         haddr = vmf->address & HPAGE_PMD_MASK;
1184         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1185                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1186
1187 unlock:
1188         spin_unlock(vmf->ptl);
1189 }
1190
1191 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1192                         pmd_t orig_pmd, struct page *page)
1193 {
1194         struct vm_area_struct *vma = vmf->vma;
1195         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1196         struct mem_cgroup *memcg;
1197         pgtable_t pgtable;
1198         pmd_t _pmd;
1199         int i;
1200         vm_fault_t ret = 0;
1201         struct page **pages;
1202         struct mmu_notifier_range range;
1203
1204         pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1205                               GFP_KERNEL);
1206         if (unlikely(!pages)) {
1207                 ret |= VM_FAULT_OOM;
1208                 goto out;
1209         }
1210
1211         for (i = 0; i < HPAGE_PMD_NR; i++) {
1212                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1213                                                vmf->address, page_to_nid(page));
1214                 if (unlikely(!pages[i] ||
1215                              mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1216                                      GFP_KERNEL, &memcg, false))) {
1217                         if (pages[i])
1218                                 put_page(pages[i]);
1219                         while (--i >= 0) {
1220                                 memcg = (void *)page_private(pages[i]);
1221                                 set_page_private(pages[i], 0);
1222                                 mem_cgroup_cancel_charge(pages[i], memcg,
1223                                                 false);
1224                                 put_page(pages[i]);
1225                         }
1226                         kfree(pages);
1227                         ret |= VM_FAULT_OOM;
1228                         goto out;
1229                 }
1230                 set_page_private(pages[i], (unsigned long)memcg);
1231         }
1232
1233         for (i = 0; i < HPAGE_PMD_NR; i++) {
1234                 copy_user_highpage(pages[i], page + i,
1235                                    haddr + PAGE_SIZE * i, vma);
1236                 __SetPageUptodate(pages[i]);
1237                 cond_resched();
1238         }
1239
1240         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1241                                 haddr, haddr + HPAGE_PMD_SIZE);
1242         mmu_notifier_invalidate_range_start(&range);
1243
1244         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1245         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1246                 goto out_free_pages;
1247         VM_BUG_ON_PAGE(!PageHead(page), page);
1248
1249         /*
1250          * Leave pmd empty until pte is filled note we must notify here as
1251          * concurrent CPU thread might write to new page before the call to
1252          * mmu_notifier_invalidate_range_end() happens which can lead to a
1253          * device seeing memory write in different order than CPU.
1254          *
1255          * See Documentation/vm/mmu_notifier.rst
1256          */
1257         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1258
1259         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1260         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1261
1262         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1263                 pte_t entry;
1264                 entry = mk_pte(pages[i], vma->vm_page_prot);
1265                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1266                 memcg = (void *)page_private(pages[i]);
1267                 set_page_private(pages[i], 0);
1268                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1269                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1270                 lru_cache_add_active_or_unevictable(pages[i], vma);
1271                 vmf->pte = pte_offset_map(&_pmd, haddr);
1272                 VM_BUG_ON(!pte_none(*vmf->pte));
1273                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1274                 pte_unmap(vmf->pte);
1275         }
1276         kfree(pages);
1277
1278         smp_wmb(); /* make pte visible before pmd */
1279         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1280         page_remove_rmap(page, true);
1281         spin_unlock(vmf->ptl);
1282
1283         /*
1284          * No need to double call mmu_notifier->invalidate_range() callback as
1285          * the above pmdp_huge_clear_flush_notify() did already call it.
1286          */
1287         mmu_notifier_invalidate_range_only_end(&range);
1288
1289         ret |= VM_FAULT_WRITE;
1290         put_page(page);
1291
1292 out:
1293         return ret;
1294
1295 out_free_pages:
1296         spin_unlock(vmf->ptl);
1297         mmu_notifier_invalidate_range_end(&range);
1298         for (i = 0; i < HPAGE_PMD_NR; i++) {
1299                 memcg = (void *)page_private(pages[i]);
1300                 set_page_private(pages[i], 0);
1301                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1302                 put_page(pages[i]);
1303         }
1304         kfree(pages);
1305         goto out;
1306 }
1307
1308 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1309 {
1310         struct vm_area_struct *vma = vmf->vma;
1311         struct page *page = NULL, *new_page;
1312         struct mem_cgroup *memcg;
1313         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1314         struct mmu_notifier_range range;
1315         gfp_t huge_gfp;                 /* for allocation and charge */
1316         vm_fault_t ret = 0;
1317
1318         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1319         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1320         if (is_huge_zero_pmd(orig_pmd))
1321                 goto alloc;
1322         spin_lock(vmf->ptl);
1323         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1324                 goto out_unlock;
1325
1326         page = pmd_page(orig_pmd);
1327         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1328         /*
1329          * We can only reuse the page if nobody else maps the huge page or it's
1330          * part.
1331          */
1332         if (!trylock_page(page)) {
1333                 get_page(page);
1334                 spin_unlock(vmf->ptl);
1335                 lock_page(page);
1336                 spin_lock(vmf->ptl);
1337                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1338                         unlock_page(page);
1339                         put_page(page);
1340                         goto out_unlock;
1341                 }
1342                 put_page(page);
1343         }
1344         if (reuse_swap_page(page, NULL)) {
1345                 pmd_t entry;
1346                 entry = pmd_mkyoung(orig_pmd);
1347                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1348                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1349                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1350                 ret |= VM_FAULT_WRITE;
1351                 unlock_page(page);
1352                 goto out_unlock;
1353         }
1354         unlock_page(page);
1355         get_page(page);
1356         spin_unlock(vmf->ptl);
1357 alloc:
1358         if (__transparent_hugepage_enabled(vma) &&
1359             !transparent_hugepage_debug_cow()) {
1360                 huge_gfp = alloc_hugepage_direct_gfpmask(vma, haddr);
1361                 new_page = alloc_pages_vma(huge_gfp, HPAGE_PMD_ORDER, vma,
1362                                 haddr, numa_node_id());
1363         } else
1364                 new_page = NULL;
1365
1366         if (likely(new_page)) {
1367                 prep_transhuge_page(new_page);
1368         } else {
1369                 if (!page) {
1370                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1371                         ret |= VM_FAULT_FALLBACK;
1372                 } else {
1373                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1374                         if (ret & VM_FAULT_OOM) {
1375                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1376                                 ret |= VM_FAULT_FALLBACK;
1377                         }
1378                         put_page(page);
1379                 }
1380                 count_vm_event(THP_FAULT_FALLBACK);
1381                 goto out;
1382         }
1383
1384         if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1385                                         huge_gfp, &memcg, true))) {
1386                 put_page(new_page);
1387                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1388                 if (page)
1389                         put_page(page);
1390                 ret |= VM_FAULT_FALLBACK;
1391                 count_vm_event(THP_FAULT_FALLBACK);
1392                 goto out;
1393         }
1394
1395         count_vm_event(THP_FAULT_ALLOC);
1396         count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
1397
1398         if (!page)
1399                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1400         else
1401                 copy_user_huge_page(new_page, page, vmf->address,
1402                                     vma, HPAGE_PMD_NR);
1403         __SetPageUptodate(new_page);
1404
1405         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1406                                 haddr, haddr + HPAGE_PMD_SIZE);
1407         mmu_notifier_invalidate_range_start(&range);
1408
1409         spin_lock(vmf->ptl);
1410         if (page)
1411                 put_page(page);
1412         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1413                 spin_unlock(vmf->ptl);
1414                 mem_cgroup_cancel_charge(new_page, memcg, true);
1415                 put_page(new_page);
1416                 goto out_mn;
1417         } else {
1418                 pmd_t entry;
1419                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1420                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1421                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1422                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1423                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1424                 lru_cache_add_active_or_unevictable(new_page, vma);
1425                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1426                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1427                 if (!page) {
1428                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1429                 } else {
1430                         VM_BUG_ON_PAGE(!PageHead(page), page);
1431                         page_remove_rmap(page, true);
1432                         put_page(page);
1433                 }
1434                 ret |= VM_FAULT_WRITE;
1435         }
1436         spin_unlock(vmf->ptl);
1437 out_mn:
1438         /*
1439          * No need to double call mmu_notifier->invalidate_range() callback as
1440          * the above pmdp_huge_clear_flush_notify() did already call it.
1441          */
1442         mmu_notifier_invalidate_range_only_end(&range);
1443 out:
1444         return ret;
1445 out_unlock:
1446         spin_unlock(vmf->ptl);
1447         return ret;
1448 }
1449
1450 /*
1451  * FOLL_FORCE can write to even unwritable pmd's, but only
1452  * after we've gone through a COW cycle and they are dirty.
1453  */
1454 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1455 {
1456         return pmd_write(pmd) ||
1457                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1458 }
1459
1460 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1461                                    unsigned long addr,
1462                                    pmd_t *pmd,
1463                                    unsigned int flags)
1464 {
1465         struct mm_struct *mm = vma->vm_mm;
1466         struct page *page = NULL;
1467
1468         assert_spin_locked(pmd_lockptr(mm, pmd));
1469
1470         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1471                 goto out;
1472
1473         /* Avoid dumping huge zero page */
1474         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1475                 return ERR_PTR(-EFAULT);
1476
1477         /* Full NUMA hinting faults to serialise migration in fault paths */
1478         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1479                 goto out;
1480
1481         page = pmd_page(*pmd);
1482         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1483         if (flags & FOLL_TOUCH)
1484                 touch_pmd(vma, addr, pmd, flags);
1485         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1486                 /*
1487                  * We don't mlock() pte-mapped THPs. This way we can avoid
1488                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1489                  *
1490                  * For anon THP:
1491                  *
1492                  * In most cases the pmd is the only mapping of the page as we
1493                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1494                  * writable private mappings in populate_vma_page_range().
1495                  *
1496                  * The only scenario when we have the page shared here is if we
1497                  * mlocking read-only mapping shared over fork(). We skip
1498                  * mlocking such pages.
1499                  *
1500                  * For file THP:
1501                  *
1502                  * We can expect PageDoubleMap() to be stable under page lock:
1503                  * for file pages we set it in page_add_file_rmap(), which
1504                  * requires page to be locked.
1505                  */
1506
1507                 if (PageAnon(page) && compound_mapcount(page) != 1)
1508                         goto skip_mlock;
1509                 if (PageDoubleMap(page) || !page->mapping)
1510                         goto skip_mlock;
1511                 if (!trylock_page(page))
1512                         goto skip_mlock;
1513                 lru_add_drain();
1514                 if (page->mapping && !PageDoubleMap(page))
1515                         mlock_vma_page(page);
1516                 unlock_page(page);
1517         }
1518 skip_mlock:
1519         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1520         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1521         if (flags & FOLL_GET)
1522                 get_page(page);
1523
1524 out:
1525         return page;
1526 }
1527
1528 /* NUMA hinting page fault entry point for trans huge pmds */
1529 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1530 {
1531         struct vm_area_struct *vma = vmf->vma;
1532         struct anon_vma *anon_vma = NULL;
1533         struct page *page;
1534         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1535         int page_nid = NUMA_NO_NODE, this_nid = numa_node_id();
1536         int target_nid, last_cpupid = -1;
1537         bool page_locked;
1538         bool migrated = false;
1539         bool was_writable;
1540         int flags = 0;
1541
1542         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1543         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1544                 goto out_unlock;
1545
1546         /*
1547          * If there are potential migrations, wait for completion and retry
1548          * without disrupting NUMA hinting information. Do not relock and
1549          * check_same as the page may no longer be mapped.
1550          */
1551         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1552                 page = pmd_page(*vmf->pmd);
1553                 if (!get_page_unless_zero(page))
1554                         goto out_unlock;
1555                 spin_unlock(vmf->ptl);
1556                 put_and_wait_on_page_locked(page);
1557                 goto out;
1558         }
1559
1560         page = pmd_page(pmd);
1561         BUG_ON(is_huge_zero_page(page));
1562         page_nid = page_to_nid(page);
1563         last_cpupid = page_cpupid_last(page);
1564         count_vm_numa_event(NUMA_HINT_FAULTS);
1565         if (page_nid == this_nid) {
1566                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1567                 flags |= TNF_FAULT_LOCAL;
1568         }
1569
1570         /* See similar comment in do_numa_page for explanation */
1571         if (!pmd_savedwrite(pmd))
1572                 flags |= TNF_NO_GROUP;
1573
1574         /*
1575          * Acquire the page lock to serialise THP migrations but avoid dropping
1576          * page_table_lock if at all possible
1577          */
1578         page_locked = trylock_page(page);
1579         target_nid = mpol_misplaced(page, vma, haddr);
1580         if (target_nid == NUMA_NO_NODE) {
1581                 /* If the page was locked, there are no parallel migrations */
1582                 if (page_locked)
1583                         goto clear_pmdnuma;
1584         }
1585
1586         /* Migration could have started since the pmd_trans_migrating check */
1587         if (!page_locked) {
1588                 page_nid = NUMA_NO_NODE;
1589                 if (!get_page_unless_zero(page))
1590                         goto out_unlock;
1591                 spin_unlock(vmf->ptl);
1592                 put_and_wait_on_page_locked(page);
1593                 goto out;
1594         }
1595
1596         /*
1597          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1598          * to serialises splits
1599          */
1600         get_page(page);
1601         spin_unlock(vmf->ptl);
1602         anon_vma = page_lock_anon_vma_read(page);
1603
1604         /* Confirm the PMD did not change while page_table_lock was released */
1605         spin_lock(vmf->ptl);
1606         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1607                 unlock_page(page);
1608                 put_page(page);
1609                 page_nid = NUMA_NO_NODE;
1610                 goto out_unlock;
1611         }
1612
1613         /* Bail if we fail to protect against THP splits for any reason */
1614         if (unlikely(!anon_vma)) {
1615                 put_page(page);
1616                 page_nid = NUMA_NO_NODE;
1617                 goto clear_pmdnuma;
1618         }
1619
1620         /*
1621          * Since we took the NUMA fault, we must have observed the !accessible
1622          * bit. Make sure all other CPUs agree with that, to avoid them
1623          * modifying the page we're about to migrate.
1624          *
1625          * Must be done under PTL such that we'll observe the relevant
1626          * inc_tlb_flush_pending().
1627          *
1628          * We are not sure a pending tlb flush here is for a huge page
1629          * mapping or not. Hence use the tlb range variant
1630          */
1631         if (mm_tlb_flush_pending(vma->vm_mm)) {
1632                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1633                 /*
1634                  * change_huge_pmd() released the pmd lock before
1635                  * invalidating the secondary MMUs sharing the primary
1636                  * MMU pagetables (with ->invalidate_range()). The
1637                  * mmu_notifier_invalidate_range_end() (which
1638                  * internally calls ->invalidate_range()) in
1639                  * change_pmd_range() will run after us, so we can't
1640                  * rely on it here and we need an explicit invalidate.
1641                  */
1642                 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1643                                               haddr + HPAGE_PMD_SIZE);
1644         }
1645
1646         /*
1647          * Migrate the THP to the requested node, returns with page unlocked
1648          * and access rights restored.
1649          */
1650         spin_unlock(vmf->ptl);
1651
1652         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1653                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1654         if (migrated) {
1655                 flags |= TNF_MIGRATED;
1656                 page_nid = target_nid;
1657         } else
1658                 flags |= TNF_MIGRATE_FAIL;
1659
1660         goto out;
1661 clear_pmdnuma:
1662         BUG_ON(!PageLocked(page));
1663         was_writable = pmd_savedwrite(pmd);
1664         pmd = pmd_modify(pmd, vma->vm_page_prot);
1665         pmd = pmd_mkyoung(pmd);
1666         if (was_writable)
1667                 pmd = pmd_mkwrite(pmd);
1668         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1669         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1670         unlock_page(page);
1671 out_unlock:
1672         spin_unlock(vmf->ptl);
1673
1674 out:
1675         if (anon_vma)
1676                 page_unlock_anon_vma_read(anon_vma);
1677
1678         if (page_nid != NUMA_NO_NODE)
1679                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1680                                 flags);
1681
1682         return 0;
1683 }
1684
1685 /*
1686  * Return true if we do MADV_FREE successfully on entire pmd page.
1687  * Otherwise, return false.
1688  */
1689 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1690                 pmd_t *pmd, unsigned long addr, unsigned long next)
1691 {
1692         spinlock_t *ptl;
1693         pmd_t orig_pmd;
1694         struct page *page;
1695         struct mm_struct *mm = tlb->mm;
1696         bool ret = false;
1697
1698         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1699
1700         ptl = pmd_trans_huge_lock(pmd, vma);
1701         if (!ptl)
1702                 goto out_unlocked;
1703
1704         orig_pmd = *pmd;
1705         if (is_huge_zero_pmd(orig_pmd))
1706                 goto out;
1707
1708         if (unlikely(!pmd_present(orig_pmd))) {
1709                 VM_BUG_ON(thp_migration_supported() &&
1710                                   !is_pmd_migration_entry(orig_pmd));
1711                 goto out;
1712         }
1713
1714         page = pmd_page(orig_pmd);
1715         /*
1716          * If other processes are mapping this page, we couldn't discard
1717          * the page unless they all do MADV_FREE so let's skip the page.
1718          */
1719         if (page_mapcount(page) != 1)
1720                 goto out;
1721
1722         if (!trylock_page(page))
1723                 goto out;
1724
1725         /*
1726          * If user want to discard part-pages of THP, split it so MADV_FREE
1727          * will deactivate only them.
1728          */
1729         if (next - addr != HPAGE_PMD_SIZE) {
1730                 get_page(page);
1731                 spin_unlock(ptl);
1732                 split_huge_page(page);
1733                 unlock_page(page);
1734                 put_page(page);
1735                 goto out_unlocked;
1736         }
1737
1738         if (PageDirty(page))
1739                 ClearPageDirty(page);
1740         unlock_page(page);
1741
1742         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1743                 pmdp_invalidate(vma, addr, pmd);
1744                 orig_pmd = pmd_mkold(orig_pmd);
1745                 orig_pmd = pmd_mkclean(orig_pmd);
1746
1747                 set_pmd_at(mm, addr, pmd, orig_pmd);
1748                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1749         }
1750
1751         mark_page_lazyfree(page);
1752         ret = true;
1753 out:
1754         spin_unlock(ptl);
1755 out_unlocked:
1756         return ret;
1757 }
1758
1759 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1760 {
1761         pgtable_t pgtable;
1762
1763         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1764         pte_free(mm, pgtable);
1765         mm_dec_nr_ptes(mm);
1766 }
1767
1768 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1769                  pmd_t *pmd, unsigned long addr)
1770 {
1771         pmd_t orig_pmd;
1772         spinlock_t *ptl;
1773
1774         tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1775
1776         ptl = __pmd_trans_huge_lock(pmd, vma);
1777         if (!ptl)
1778                 return 0;
1779         /*
1780          * For architectures like ppc64 we look at deposited pgtable
1781          * when calling pmdp_huge_get_and_clear. So do the
1782          * pgtable_trans_huge_withdraw after finishing pmdp related
1783          * operations.
1784          */
1785         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1786                         tlb->fullmm);
1787         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1788         if (vma_is_dax(vma)) {
1789                 if (arch_needs_pgtable_deposit())
1790                         zap_deposited_table(tlb->mm, pmd);
1791                 spin_unlock(ptl);
1792                 if (is_huge_zero_pmd(orig_pmd))
1793                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1794         } else if (is_huge_zero_pmd(orig_pmd)) {
1795                 zap_deposited_table(tlb->mm, pmd);
1796                 spin_unlock(ptl);
1797                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1798         } else {
1799                 struct page *page = NULL;
1800                 int flush_needed = 1;
1801
1802                 if (pmd_present(orig_pmd)) {
1803                         page = pmd_page(orig_pmd);
1804                         page_remove_rmap(page, true);
1805                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1806                         VM_BUG_ON_PAGE(!PageHead(page), page);
1807                 } else if (thp_migration_supported()) {
1808                         swp_entry_t entry;
1809
1810                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1811                         entry = pmd_to_swp_entry(orig_pmd);
1812                         page = pfn_to_page(swp_offset(entry));
1813                         flush_needed = 0;
1814                 } else
1815                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1816
1817                 if (PageAnon(page)) {
1818                         zap_deposited_table(tlb->mm, pmd);
1819                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1820                 } else {
1821                         if (arch_needs_pgtable_deposit())
1822                                 zap_deposited_table(tlb->mm, pmd);
1823                         add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1824                 }
1825
1826                 spin_unlock(ptl);
1827                 if (flush_needed)
1828                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1829         }
1830         return 1;
1831 }
1832
1833 #ifndef pmd_move_must_withdraw
1834 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1835                                          spinlock_t *old_pmd_ptl,
1836                                          struct vm_area_struct *vma)
1837 {
1838         /*
1839          * With split pmd lock we also need to move preallocated
1840          * PTE page table if new_pmd is on different PMD page table.
1841          *
1842          * We also don't deposit and withdraw tables for file pages.
1843          */
1844         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1845 }
1846 #endif
1847
1848 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1849 {
1850 #ifdef CONFIG_MEM_SOFT_DIRTY
1851         if (unlikely(is_pmd_migration_entry(pmd)))
1852                 pmd = pmd_swp_mksoft_dirty(pmd);
1853         else if (pmd_present(pmd))
1854                 pmd = pmd_mksoft_dirty(pmd);
1855 #endif
1856         return pmd;
1857 }
1858
1859 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1860                   unsigned long new_addr, unsigned long old_end,
1861                   pmd_t *old_pmd, pmd_t *new_pmd)
1862 {
1863         spinlock_t *old_ptl, *new_ptl;
1864         pmd_t pmd;
1865         struct mm_struct *mm = vma->vm_mm;
1866         bool force_flush = false;
1867
1868         if ((old_addr & ~HPAGE_PMD_MASK) ||
1869             (new_addr & ~HPAGE_PMD_MASK) ||
1870             old_end - old_addr < HPAGE_PMD_SIZE)
1871                 return false;
1872
1873         /*
1874          * The destination pmd shouldn't be established, free_pgtables()
1875          * should have release it.
1876          */
1877         if (WARN_ON(!pmd_none(*new_pmd))) {
1878                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1879                 return false;
1880         }
1881
1882         /*
1883          * We don't have to worry about the ordering of src and dst
1884          * ptlocks because exclusive mmap_sem prevents deadlock.
1885          */
1886         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1887         if (old_ptl) {
1888                 new_ptl = pmd_lockptr(mm, new_pmd);
1889                 if (new_ptl != old_ptl)
1890                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1891                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1892                 if (pmd_present(pmd))
1893                         force_flush = true;
1894                 VM_BUG_ON(!pmd_none(*new_pmd));
1895
1896                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1897                         pgtable_t pgtable;
1898                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1899                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1900                 }
1901                 pmd = move_soft_dirty_pmd(pmd);
1902                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1903                 if (force_flush)
1904                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1905                 if (new_ptl != old_ptl)
1906                         spin_unlock(new_ptl);
1907                 spin_unlock(old_ptl);
1908                 return true;
1909         }
1910         return false;
1911 }
1912
1913 /*
1914  * Returns
1915  *  - 0 if PMD could not be locked
1916  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1917  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1918  */
1919 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1920                 unsigned long addr, pgprot_t newprot, int prot_numa)
1921 {
1922         struct mm_struct *mm = vma->vm_mm;
1923         spinlock_t *ptl;
1924         pmd_t entry;
1925         bool preserve_write;
1926         int ret;
1927
1928         ptl = __pmd_trans_huge_lock(pmd, vma);
1929         if (!ptl)
1930                 return 0;
1931
1932         preserve_write = prot_numa && pmd_write(*pmd);
1933         ret = 1;
1934
1935 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1936         if (is_swap_pmd(*pmd)) {
1937                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1938
1939                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1940                 if (is_write_migration_entry(entry)) {
1941                         pmd_t newpmd;
1942                         /*
1943                          * A protection check is difficult so
1944                          * just be safe and disable write
1945                          */
1946                         make_migration_entry_read(&entry);
1947                         newpmd = swp_entry_to_pmd(entry);
1948                         if (pmd_swp_soft_dirty(*pmd))
1949                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1950                         set_pmd_at(mm, addr, pmd, newpmd);
1951                 }
1952                 goto unlock;
1953         }
1954 #endif
1955
1956         /*
1957          * Avoid trapping faults against the zero page. The read-only
1958          * data is likely to be read-cached on the local CPU and
1959          * local/remote hits to the zero page are not interesting.
1960          */
1961         if (prot_numa && is_huge_zero_pmd(*pmd))
1962                 goto unlock;
1963
1964         if (prot_numa && pmd_protnone(*pmd))
1965                 goto unlock;
1966
1967         /*
1968          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1969          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1970          * which is also under down_read(mmap_sem):
1971          *
1972          *      CPU0:                           CPU1:
1973          *                              change_huge_pmd(prot_numa=1)
1974          *                               pmdp_huge_get_and_clear_notify()
1975          * madvise_dontneed()
1976          *  zap_pmd_range()
1977          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1978          *   // skip the pmd
1979          *                               set_pmd_at();
1980          *                               // pmd is re-established
1981          *
1982          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1983          * which may break userspace.
1984          *
1985          * pmdp_invalidate() is required to make sure we don't miss
1986          * dirty/young flags set by hardware.
1987          */
1988         entry = pmdp_invalidate(vma, addr, pmd);
1989
1990         entry = pmd_modify(entry, newprot);
1991         if (preserve_write)
1992                 entry = pmd_mk_savedwrite(entry);
1993         ret = HPAGE_PMD_NR;
1994         set_pmd_at(mm, addr, pmd, entry);
1995         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1996 unlock:
1997         spin_unlock(ptl);
1998         return ret;
1999 }
2000
2001 /*
2002  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
2003  *
2004  * Note that if it returns page table lock pointer, this routine returns without
2005  * unlocking page table lock. So callers must unlock it.
2006  */
2007 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
2008 {
2009         spinlock_t *ptl;
2010         ptl = pmd_lock(vma->vm_mm, pmd);
2011         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
2012                         pmd_devmap(*pmd)))
2013                 return ptl;
2014         spin_unlock(ptl);
2015         return NULL;
2016 }
2017
2018 /*
2019  * Returns true if a given pud maps a thp, false otherwise.
2020  *
2021  * Note that if it returns true, this routine returns without unlocking page
2022  * table lock. So callers must unlock it.
2023  */
2024 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
2025 {
2026         spinlock_t *ptl;
2027
2028         ptl = pud_lock(vma->vm_mm, pud);
2029         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
2030                 return ptl;
2031         spin_unlock(ptl);
2032         return NULL;
2033 }
2034
2035 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
2036 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
2037                  pud_t *pud, unsigned long addr)
2038 {
2039         spinlock_t *ptl;
2040
2041         ptl = __pud_trans_huge_lock(pud, vma);
2042         if (!ptl)
2043                 return 0;
2044         /*
2045          * For architectures like ppc64 we look at deposited pgtable
2046          * when calling pudp_huge_get_and_clear. So do the
2047          * pgtable_trans_huge_withdraw after finishing pudp related
2048          * operations.
2049          */
2050         pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
2051         tlb_remove_pud_tlb_entry(tlb, pud, addr);
2052         if (vma_is_dax(vma)) {
2053                 spin_unlock(ptl);
2054                 /* No zero page support yet */
2055         } else {
2056                 /* No support for anonymous PUD pages yet */
2057                 BUG();
2058         }
2059         return 1;
2060 }
2061
2062 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2063                 unsigned long haddr)
2064 {
2065         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2066         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2067         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2068         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2069
2070         count_vm_event(THP_SPLIT_PUD);
2071
2072         pudp_huge_clear_flush_notify(vma, haddr, pud);
2073 }
2074
2075 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2076                 unsigned long address)
2077 {
2078         spinlock_t *ptl;
2079         struct mmu_notifier_range range;
2080
2081         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2082                                 address & HPAGE_PUD_MASK,
2083                                 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2084         mmu_notifier_invalidate_range_start(&range);
2085         ptl = pud_lock(vma->vm_mm, pud);
2086         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2087                 goto out;
2088         __split_huge_pud_locked(vma, pud, range.start);
2089
2090 out:
2091         spin_unlock(ptl);
2092         /*
2093          * No need to double call mmu_notifier->invalidate_range() callback as
2094          * the above pudp_huge_clear_flush_notify() did already call it.
2095          */
2096         mmu_notifier_invalidate_range_only_end(&range);
2097 }
2098 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2099
2100 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2101                 unsigned long haddr, pmd_t *pmd)
2102 {
2103         struct mm_struct *mm = vma->vm_mm;
2104         pgtable_t pgtable;
2105         pmd_t _pmd;
2106         int i;
2107
2108         /*
2109          * Leave pmd empty until pte is filled note that it is fine to delay
2110          * notification until mmu_notifier_invalidate_range_end() as we are
2111          * replacing a zero pmd write protected page with a zero pte write
2112          * protected page.
2113          *
2114          * See Documentation/vm/mmu_notifier.rst
2115          */
2116         pmdp_huge_clear_flush(vma, haddr, pmd);
2117
2118         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2119         pmd_populate(mm, &_pmd, pgtable);
2120
2121         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2122                 pte_t *pte, entry;
2123                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2124                 entry = pte_mkspecial(entry);
2125                 pte = pte_offset_map(&_pmd, haddr);
2126                 VM_BUG_ON(!pte_none(*pte));
2127                 set_pte_at(mm, haddr, pte, entry);
2128                 pte_unmap(pte);
2129         }
2130         smp_wmb(); /* make pte visible before pmd */
2131         pmd_populate(mm, pmd, pgtable);
2132 }
2133
2134 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2135                 unsigned long haddr, bool freeze)
2136 {
2137         struct mm_struct *mm = vma->vm_mm;
2138         struct page *page;
2139         pgtable_t pgtable;
2140         pmd_t old_pmd, _pmd;
2141         bool young, write, soft_dirty, pmd_migration = false;
2142         unsigned long addr;
2143         int i;
2144
2145         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2146         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2147         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2148         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2149                                 && !pmd_devmap(*pmd));
2150
2151         count_vm_event(THP_SPLIT_PMD);
2152
2153         if (!vma_is_anonymous(vma)) {
2154                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2155                 /*
2156                  * We are going to unmap this huge page. So
2157                  * just go ahead and zap it
2158                  */
2159                 if (arch_needs_pgtable_deposit())
2160                         zap_deposited_table(mm, pmd);
2161                 if (vma_is_dax(vma))
2162                         return;
2163                 page = pmd_page(_pmd);
2164                 if (!PageDirty(page) && pmd_dirty(_pmd))
2165                         set_page_dirty(page);
2166                 if (!PageReferenced(page) && pmd_young(_pmd))
2167                         SetPageReferenced(page);
2168                 page_remove_rmap(page, true);
2169                 put_page(page);
2170                 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2171                 return;
2172         } else if (is_huge_zero_pmd(*pmd)) {
2173                 /*
2174                  * FIXME: Do we want to invalidate secondary mmu by calling
2175                  * mmu_notifier_invalidate_range() see comments below inside
2176                  * __split_huge_pmd() ?
2177                  *
2178                  * We are going from a zero huge page write protected to zero
2179                  * small page also write protected so it does not seems useful
2180                  * to invalidate secondary mmu at this time.
2181                  */
2182                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2183         }
2184
2185         /*
2186          * Up to this point the pmd is present and huge and userland has the
2187          * whole access to the hugepage during the split (which happens in
2188          * place). If we overwrite the pmd with the not-huge version pointing
2189          * to the pte here (which of course we could if all CPUs were bug
2190          * free), userland could trigger a small page size TLB miss on the
2191          * small sized TLB while the hugepage TLB entry is still established in
2192          * the huge TLB. Some CPU doesn't like that.
2193          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2194          * 383 on page 93. Intel should be safe but is also warns that it's
2195          * only safe if the permission and cache attributes of the two entries
2196          * loaded in the two TLB is identical (which should be the case here).
2197          * But it is generally safer to never allow small and huge TLB entries
2198          * for the same virtual address to be loaded simultaneously. So instead
2199          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2200          * current pmd notpresent (atomically because here the pmd_trans_huge
2201          * must remain set at all times on the pmd until the split is complete
2202          * for this pmd), then we flush the SMP TLB and finally we write the
2203          * non-huge version of the pmd entry with pmd_populate.
2204          */
2205         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2206
2207         pmd_migration = is_pmd_migration_entry(old_pmd);
2208         if (unlikely(pmd_migration)) {
2209                 swp_entry_t entry;
2210
2211                 entry = pmd_to_swp_entry(old_pmd);
2212                 page = pfn_to_page(swp_offset(entry));
2213                 write = is_write_migration_entry(entry);
2214                 young = false;
2215                 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2216         } else {
2217                 page = pmd_page(old_pmd);
2218                 if (pmd_dirty(old_pmd))
2219                         SetPageDirty(page);
2220                 write = pmd_write(old_pmd);
2221                 young = pmd_young(old_pmd);
2222                 soft_dirty = pmd_soft_dirty(old_pmd);
2223         }
2224         VM_BUG_ON_PAGE(!page_count(page), page);
2225         page_ref_add(page, HPAGE_PMD_NR - 1);
2226
2227         /*
2228          * Withdraw the table only after we mark the pmd entry invalid.
2229          * This's critical for some architectures (Power).
2230          */
2231         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2232         pmd_populate(mm, &_pmd, pgtable);
2233
2234         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2235                 pte_t entry, *pte;
2236                 /*
2237                  * Note that NUMA hinting access restrictions are not
2238                  * transferred to avoid any possibility of altering
2239                  * permissions across VMAs.
2240                  */
2241                 if (freeze || pmd_migration) {
2242                         swp_entry_t swp_entry;
2243                         swp_entry = make_migration_entry(page + i, write);
2244                         entry = swp_entry_to_pte(swp_entry);
2245                         if (soft_dirty)
2246                                 entry = pte_swp_mksoft_dirty(entry);
2247                 } else {
2248                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2249                         entry = maybe_mkwrite(entry, vma);
2250                         if (!write)
2251                                 entry = pte_wrprotect(entry);
2252                         if (!young)
2253                                 entry = pte_mkold(entry);
2254                         if (soft_dirty)
2255                                 entry = pte_mksoft_dirty(entry);
2256                 }
2257                 pte = pte_offset_map(&_pmd, addr);
2258                 BUG_ON(!pte_none(*pte));
2259                 set_pte_at(mm, addr, pte, entry);
2260                 atomic_inc(&page[i]._mapcount);
2261                 pte_unmap(pte);
2262         }
2263
2264         /*
2265          * Set PG_double_map before dropping compound_mapcount to avoid
2266          * false-negative page_mapped().
2267          */
2268         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2269                 for (i = 0; i < HPAGE_PMD_NR; i++)
2270                         atomic_inc(&page[i]._mapcount);
2271         }
2272
2273         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2274                 /* Last compound_mapcount is gone. */
2275                 __dec_node_page_state(page, NR_ANON_THPS);
2276                 if (TestClearPageDoubleMap(page)) {
2277                         /* No need in mapcount reference anymore */
2278                         for (i = 0; i < HPAGE_PMD_NR; i++)
2279                                 atomic_dec(&page[i]._mapcount);
2280                 }
2281         }
2282
2283         smp_wmb(); /* make pte visible before pmd */
2284         pmd_populate(mm, pmd, pgtable);
2285
2286         if (freeze) {
2287                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2288                         page_remove_rmap(page + i, false);
2289                         put_page(page + i);
2290                 }
2291         }
2292 }
2293
2294 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2295                 unsigned long address, bool freeze, struct page *page)
2296 {
2297         spinlock_t *ptl;
2298         struct mmu_notifier_range range;
2299
2300         mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2301                                 address & HPAGE_PMD_MASK,
2302                                 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2303         mmu_notifier_invalidate_range_start(&range);
2304         ptl = pmd_lock(vma->vm_mm, pmd);
2305
2306         /*
2307          * If caller asks to setup a migration entries, we need a page to check
2308          * pmd against. Otherwise we can end up replacing wrong page.
2309          */
2310         VM_BUG_ON(freeze && !page);
2311         if (page && page != pmd_page(*pmd))
2312                 goto out;
2313
2314         if (pmd_trans_huge(*pmd)) {
2315                 page = pmd_page(*pmd);
2316                 if (PageMlocked(page))
2317                         clear_page_mlock(page);
2318         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2319                 goto out;
2320         __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2321 out:
2322         spin_unlock(ptl);
2323         /*
2324          * No need to double call mmu_notifier->invalidate_range() callback.
2325          * They are 3 cases to consider inside __split_huge_pmd_locked():
2326          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2327          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2328          *    fault will trigger a flush_notify before pointing to a new page
2329          *    (it is fine if the secondary mmu keeps pointing to the old zero
2330          *    page in the meantime)
2331          *  3) Split a huge pmd into pte pointing to the same page. No need
2332          *     to invalidate secondary tlb entry they are all still valid.
2333          *     any further changes to individual pte will notify. So no need
2334          *     to call mmu_notifier->invalidate_range()
2335          */
2336         mmu_notifier_invalidate_range_only_end(&range);
2337 }
2338
2339 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2340                 bool freeze, struct page *page)
2341 {
2342         pgd_t *pgd;
2343         p4d_t *p4d;
2344         pud_t *pud;
2345         pmd_t *pmd;
2346
2347         pgd = pgd_offset(vma->vm_mm, address);
2348         if (!pgd_present(*pgd))
2349                 return;
2350
2351         p4d = p4d_offset(pgd, address);
2352         if (!p4d_present(*p4d))
2353                 return;
2354
2355         pud = pud_offset(p4d, address);
2356         if (!pud_present(*pud))
2357                 return;
2358
2359         pmd = pmd_offset(pud, address);
2360
2361         __split_huge_pmd(vma, pmd, address, freeze, page);
2362 }
2363
2364 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2365                              unsigned long start,
2366                              unsigned long end,
2367                              long adjust_next)
2368 {
2369         /*
2370          * If the new start address isn't hpage aligned and it could
2371          * previously contain an hugepage: check if we need to split
2372          * an huge pmd.
2373          */
2374         if (start & ~HPAGE_PMD_MASK &&
2375             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2376             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2377                 split_huge_pmd_address(vma, start, false, NULL);
2378
2379         /*
2380          * If the new end address isn't hpage aligned and it could
2381          * previously contain an hugepage: check if we need to split
2382          * an huge pmd.
2383          */
2384         if (end & ~HPAGE_PMD_MASK &&
2385             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2386             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2387                 split_huge_pmd_address(vma, end, false, NULL);
2388
2389         /*
2390          * If we're also updating the vma->vm_next->vm_start, if the new
2391          * vm_next->vm_start isn't page aligned and it could previously
2392          * contain an hugepage: check if we need to split an huge pmd.
2393          */
2394         if (adjust_next > 0) {
2395                 struct vm_area_struct *next = vma->vm_next;
2396                 unsigned long nstart = next->vm_start;
2397                 nstart += adjust_next << PAGE_SHIFT;
2398                 if (nstart & ~HPAGE_PMD_MASK &&
2399                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2400                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2401                         split_huge_pmd_address(next, nstart, false, NULL);
2402         }
2403 }
2404
2405 static void unmap_page(struct page *page)
2406 {
2407         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2408                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2409         bool unmap_success;
2410
2411         VM_BUG_ON_PAGE(!PageHead(page), page);
2412
2413         if (PageAnon(page))
2414                 ttu_flags |= TTU_SPLIT_FREEZE;
2415
2416         unmap_success = try_to_unmap(page, ttu_flags);
2417         VM_BUG_ON_PAGE(!unmap_success, page);
2418 }
2419
2420 static void remap_page(struct page *page)
2421 {
2422         int i;
2423         if (PageTransHuge(page)) {
2424                 remove_migration_ptes(page, page, true);
2425         } else {
2426                 for (i = 0; i < HPAGE_PMD_NR; i++)
2427                         remove_migration_ptes(page + i, page + i, true);
2428         }
2429 }
2430
2431 static void __split_huge_page_tail(struct page *head, int tail,
2432                 struct lruvec *lruvec, struct list_head *list)
2433 {
2434         struct page *page_tail = head + tail;
2435
2436         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2437
2438         /*
2439          * Clone page flags before unfreezing refcount.
2440          *
2441          * After successful get_page_unless_zero() might follow flags change,
2442          * for exmaple lock_page() which set PG_waiters.
2443          */
2444         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2445         page_tail->flags |= (head->flags &
2446                         ((1L << PG_referenced) |
2447                          (1L << PG_swapbacked) |
2448                          (1L << PG_swapcache) |
2449                          (1L << PG_mlocked) |
2450                          (1L << PG_uptodate) |
2451                          (1L << PG_active) |
2452                          (1L << PG_workingset) |
2453                          (1L << PG_locked) |
2454                          (1L << PG_unevictable) |
2455                          (1L << PG_dirty)));
2456
2457         /* ->mapping in first tail page is compound_mapcount */
2458         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2459                         page_tail);
2460         page_tail->mapping = head->mapping;
2461         page_tail->index = head->index + tail;
2462
2463         /* Page flags must be visible before we make the page non-compound. */
2464         smp_wmb();
2465
2466         /*
2467          * Clear PageTail before unfreezing page refcount.
2468          *
2469          * After successful get_page_unless_zero() might follow put_page()
2470          * which needs correct compound_head().
2471          */
2472         clear_compound_head(page_tail);
2473
2474         /* Finally unfreeze refcount. Additional reference from page cache. */
2475         page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2476                                           PageSwapCache(head)));
2477
2478         if (page_is_young(head))
2479                 set_page_young(page_tail);
2480         if (page_is_idle(head))
2481                 set_page_idle(page_tail);
2482
2483         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2484
2485         /*
2486          * always add to the tail because some iterators expect new
2487          * pages to show after the currently processed elements - e.g.
2488          * migrate_pages
2489          */
2490         lru_add_page_tail(head, page_tail, lruvec, list);
2491 }
2492
2493 static void __split_huge_page(struct page *page, struct list_head *list,
2494                 pgoff_t end, unsigned long flags)
2495 {
2496         struct page *head = compound_head(page);
2497         pg_data_t *pgdat = page_pgdat(head);
2498         struct lruvec *lruvec;
2499         int i;
2500
2501         lruvec = mem_cgroup_page_lruvec(head, pgdat);
2502
2503         /* complete memcg works before add pages to LRU */
2504         mem_cgroup_split_huge_fixup(head);
2505
2506         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2507                 __split_huge_page_tail(head, i, lruvec, list);
2508                 /* Some pages can be beyond i_size: drop them from page cache */
2509                 if (head[i].index >= end) {
2510                         ClearPageDirty(head + i);
2511                         __delete_from_page_cache(head + i, NULL);
2512                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2513                                 shmem_uncharge(head->mapping->host, 1);
2514                         put_page(head + i);
2515                 }
2516         }
2517
2518         ClearPageCompound(head);
2519         /* See comment in __split_huge_page_tail() */
2520         if (PageAnon(head)) {
2521                 /* Additional pin to swap cache */
2522                 if (PageSwapCache(head))
2523                         page_ref_add(head, 2);
2524                 else
2525                         page_ref_inc(head);
2526         } else {
2527                 /* Additional pin to page cache */
2528                 page_ref_add(head, 2);
2529                 xa_unlock(&head->mapping->i_pages);
2530         }
2531
2532         spin_unlock_irqrestore(&pgdat->lru_lock, flags);
2533
2534         remap_page(head);
2535
2536         for (i = 0; i < HPAGE_PMD_NR; i++) {
2537                 struct page *subpage = head + i;
2538                 if (subpage == page)
2539                         continue;
2540                 unlock_page(subpage);
2541
2542                 /*
2543                  * Subpages may be freed if there wasn't any mapping
2544                  * like if add_to_swap() is running on a lru page that
2545                  * had its mapping zapped. And freeing these pages
2546                  * requires taking the lru_lock so we do the put_page
2547                  * of the tail pages after the split is complete.
2548                  */
2549                 put_page(subpage);
2550         }
2551 }
2552
2553 int total_mapcount(struct page *page)
2554 {
2555         int i, compound, ret;
2556
2557         VM_BUG_ON_PAGE(PageTail(page), page);
2558
2559         if (likely(!PageCompound(page)))
2560                 return atomic_read(&page->_mapcount) + 1;
2561
2562         compound = compound_mapcount(page);
2563         if (PageHuge(page))
2564                 return compound;
2565         ret = compound;
2566         for (i = 0; i < HPAGE_PMD_NR; i++)
2567                 ret += atomic_read(&page[i]._mapcount) + 1;
2568         /* File pages has compound_mapcount included in _mapcount */
2569         if (!PageAnon(page))
2570                 return ret - compound * HPAGE_PMD_NR;
2571         if (PageDoubleMap(page))
2572                 ret -= HPAGE_PMD_NR;
2573         return ret;
2574 }
2575
2576 /*
2577  * This calculates accurately how many mappings a transparent hugepage
2578  * has (unlike page_mapcount() which isn't fully accurate). This full
2579  * accuracy is primarily needed to know if copy-on-write faults can
2580  * reuse the page and change the mapping to read-write instead of
2581  * copying them. At the same time this returns the total_mapcount too.
2582  *
2583  * The function returns the highest mapcount any one of the subpages
2584  * has. If the return value is one, even if different processes are
2585  * mapping different subpages of the transparent hugepage, they can
2586  * all reuse it, because each process is reusing a different subpage.
2587  *
2588  * The total_mapcount is instead counting all virtual mappings of the
2589  * subpages. If the total_mapcount is equal to "one", it tells the
2590  * caller all mappings belong to the same "mm" and in turn the
2591  * anon_vma of the transparent hugepage can become the vma->anon_vma
2592  * local one as no other process may be mapping any of the subpages.
2593  *
2594  * It would be more accurate to replace page_mapcount() with
2595  * page_trans_huge_mapcount(), however we only use
2596  * page_trans_huge_mapcount() in the copy-on-write faults where we
2597  * need full accuracy to avoid breaking page pinning, because
2598  * page_trans_huge_mapcount() is slower than page_mapcount().
2599  */
2600 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2601 {
2602         int i, ret, _total_mapcount, mapcount;
2603
2604         /* hugetlbfs shouldn't call it */
2605         VM_BUG_ON_PAGE(PageHuge(page), page);
2606
2607         if (likely(!PageTransCompound(page))) {
2608                 mapcount = atomic_read(&page->_mapcount) + 1;
2609                 if (total_mapcount)
2610                         *total_mapcount = mapcount;
2611                 return mapcount;
2612         }
2613
2614         page = compound_head(page);
2615
2616         _total_mapcount = ret = 0;
2617         for (i = 0; i < HPAGE_PMD_NR; i++) {
2618                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2619                 ret = max(ret, mapcount);
2620                 _total_mapcount += mapcount;
2621         }
2622         if (PageDoubleMap(page)) {
2623                 ret -= 1;
2624                 _total_mapcount -= HPAGE_PMD_NR;
2625         }
2626         mapcount = compound_mapcount(page);
2627         ret += mapcount;
2628         _total_mapcount += mapcount;
2629         if (total_mapcount)
2630                 *total_mapcount = _total_mapcount;
2631         return ret;
2632 }
2633
2634 /* Racy check whether the huge page can be split */
2635 bool can_split_huge_page(struct page *page, int *pextra_pins)
2636 {
2637         int extra_pins;
2638
2639         /* Additional pins from page cache */
2640         if (PageAnon(page))
2641                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2642         else
2643                 extra_pins = HPAGE_PMD_NR;
2644         if (pextra_pins)
2645                 *pextra_pins = extra_pins;
2646         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2647 }
2648
2649 /*
2650  * This function splits huge page into normal pages. @page can point to any
2651  * subpage of huge page to split. Split doesn't change the position of @page.
2652  *
2653  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2654  * The huge page must be locked.
2655  *
2656  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2657  *
2658  * Both head page and tail pages will inherit mapping, flags, and so on from
2659  * the hugepage.
2660  *
2661  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2662  * they are not mapped.
2663  *
2664  * Returns 0 if the hugepage is split successfully.
2665  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2666  * us.
2667  */
2668 int split_huge_page_to_list(struct page *page, struct list_head *list)
2669 {
2670         struct page *head = compound_head(page);
2671         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2672         struct anon_vma *anon_vma = NULL;
2673         struct address_space *mapping = NULL;
2674         int count, mapcount, extra_pins, ret;
2675         bool mlocked;
2676         unsigned long flags;
2677         pgoff_t end;
2678
2679         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2680         VM_BUG_ON_PAGE(!PageLocked(page), page);
2681         VM_BUG_ON_PAGE(!PageCompound(page), page);
2682
2683         if (PageWriteback(page))
2684                 return -EBUSY;
2685
2686         if (PageAnon(head)) {
2687                 /*
2688                  * The caller does not necessarily hold an mmap_sem that would
2689                  * prevent the anon_vma disappearing so we first we take a
2690                  * reference to it and then lock the anon_vma for write. This
2691                  * is similar to page_lock_anon_vma_read except the write lock
2692                  * is taken to serialise against parallel split or collapse
2693                  * operations.
2694                  */
2695                 anon_vma = page_get_anon_vma(head);
2696                 if (!anon_vma) {
2697                         ret = -EBUSY;
2698                         goto out;
2699                 }
2700                 end = -1;
2701                 mapping = NULL;
2702                 anon_vma_lock_write(anon_vma);
2703         } else {
2704                 mapping = head->mapping;
2705
2706                 /* Truncated ? */
2707                 if (!mapping) {
2708                         ret = -EBUSY;
2709                         goto out;
2710                 }
2711
2712                 anon_vma = NULL;
2713                 i_mmap_lock_read(mapping);
2714
2715                 /*
2716                  *__split_huge_page() may need to trim off pages beyond EOF:
2717                  * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2718                  * which cannot be nested inside the page tree lock. So note
2719                  * end now: i_size itself may be changed at any moment, but
2720                  * head page lock is good enough to serialize the trimming.
2721                  */
2722                 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2723         }
2724
2725         /*
2726          * Racy check if we can split the page, before unmap_page() will
2727          * split PMDs
2728          */
2729         if (!can_split_huge_page(head, &extra_pins)) {
2730                 ret = -EBUSY;
2731                 goto out_unlock;
2732         }
2733
2734         mlocked = PageMlocked(page);
2735         unmap_page(head);
2736         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2737
2738         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2739         if (mlocked)
2740                 lru_add_drain();
2741
2742         /* prevent PageLRU to go away from under us, and freeze lru stats */
2743         spin_lock_irqsave(&pgdata->lru_lock, flags);
2744
2745         if (mapping) {
2746                 XA_STATE(xas, &mapping->i_pages, page_index(head));
2747
2748                 /*
2749                  * Check if the head page is present in page cache.
2750                  * We assume all tail are present too, if head is there.
2751                  */
2752                 xa_lock(&mapping->i_pages);
2753                 if (xas_load(&xas) != head)
2754                         goto fail;
2755         }
2756
2757         /* Prevent deferred_split_scan() touching ->_refcount */
2758         spin_lock(&pgdata->split_queue_lock);
2759         count = page_count(head);
2760         mapcount = total_mapcount(head);
2761         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2762                 if (!list_empty(page_deferred_list(head))) {
2763                         pgdata->split_queue_len--;
2764                         list_del(page_deferred_list(head));
2765                 }
2766                 if (mapping)
2767                         __dec_node_page_state(page, NR_SHMEM_THPS);
2768                 spin_unlock(&pgdata->split_queue_lock);
2769                 __split_huge_page(page, list, end, flags);
2770                 if (PageSwapCache(head)) {
2771                         swp_entry_t entry = { .val = page_private(head) };
2772
2773                         ret = split_swap_cluster(entry);
2774                 } else
2775                         ret = 0;
2776         } else {
2777                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2778                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2779                                         mapcount, count);
2780                         if (PageTail(page))
2781                                 dump_page(head, NULL);
2782                         dump_page(page, "total_mapcount(head) > 0");
2783                         BUG();
2784                 }
2785                 spin_unlock(&pgdata->split_queue_lock);
2786 fail:           if (mapping)
2787                         xa_unlock(&mapping->i_pages);
2788                 spin_unlock_irqrestore(&pgdata->lru_lock, flags);
2789                 remap_page(head);
2790                 ret = -EBUSY;
2791         }
2792
2793 out_unlock:
2794         if (anon_vma) {
2795                 anon_vma_unlock_write(anon_vma);
2796                 put_anon_vma(anon_vma);
2797         }
2798         if (mapping)
2799                 i_mmap_unlock_read(mapping);
2800 out:
2801         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2802         return ret;
2803 }
2804
2805 void free_transhuge_page(struct page *page)
2806 {
2807         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2808         unsigned long flags;
2809
2810         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2811         if (!list_empty(page_deferred_list(page))) {
2812                 pgdata->split_queue_len--;
2813                 list_del(page_deferred_list(page));
2814         }
2815         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2816         free_compound_page(page);
2817 }
2818
2819 void deferred_split_huge_page(struct page *page)
2820 {
2821         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2822         unsigned long flags;
2823
2824         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2825
2826         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2827         if (list_empty(page_deferred_list(page))) {
2828                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2829                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2830                 pgdata->split_queue_len++;
2831         }
2832         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2833 }
2834
2835 static unsigned long deferred_split_count(struct shrinker *shrink,
2836                 struct shrink_control *sc)
2837 {
2838         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2839         return READ_ONCE(pgdata->split_queue_len);
2840 }
2841
2842 static unsigned long deferred_split_scan(struct shrinker *shrink,
2843                 struct shrink_control *sc)
2844 {
2845         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2846         unsigned long flags;
2847         LIST_HEAD(list), *pos, *next;
2848         struct page *page;
2849         int split = 0;
2850
2851         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2852         /* Take pin on all head pages to avoid freeing them under us */
2853         list_for_each_safe(pos, next, &pgdata->split_queue) {
2854                 page = list_entry((void *)pos, struct page, mapping);
2855                 page = compound_head(page);
2856                 if (get_page_unless_zero(page)) {
2857                         list_move(page_deferred_list(page), &list);
2858                 } else {
2859                         /* We lost race with put_compound_page() */
2860                         list_del_init(page_deferred_list(page));
2861                         pgdata->split_queue_len--;
2862                 }
2863                 if (!--sc->nr_to_scan)
2864                         break;
2865         }
2866         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2867
2868         list_for_each_safe(pos, next, &list) {
2869                 page = list_entry((void *)pos, struct page, mapping);
2870                 if (!trylock_page(page))
2871                         goto next;
2872                 /* split_huge_page() removes page from list on success */
2873                 if (!split_huge_page(page))
2874                         split++;
2875                 unlock_page(page);
2876 next:
2877                 put_page(page);
2878         }
2879
2880         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2881         list_splice_tail(&list, &pgdata->split_queue);
2882         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2883
2884         /*
2885          * Stop shrinker if we didn't split any page, but the queue is empty.
2886          * This can happen if pages were freed under us.
2887          */
2888         if (!split && list_empty(&pgdata->split_queue))
2889                 return SHRINK_STOP;
2890         return split;
2891 }
2892
2893 static struct shrinker deferred_split_shrinker = {
2894         .count_objects = deferred_split_count,
2895         .scan_objects = deferred_split_scan,
2896         .seeks = DEFAULT_SEEKS,
2897         .flags = SHRINKER_NUMA_AWARE,
2898 };
2899
2900 #ifdef CONFIG_DEBUG_FS
2901 static int split_huge_pages_set(void *data, u64 val)
2902 {
2903         struct zone *zone;
2904         struct page *page;
2905         unsigned long pfn, max_zone_pfn;
2906         unsigned long total = 0, split = 0;
2907
2908         if (val != 1)
2909                 return -EINVAL;
2910
2911         for_each_populated_zone(zone) {
2912                 max_zone_pfn = zone_end_pfn(zone);
2913                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2914                         if (!pfn_valid(pfn))
2915                                 continue;
2916
2917                         page = pfn_to_page(pfn);
2918                         if (!get_page_unless_zero(page))
2919                                 continue;
2920
2921                         if (zone != page_zone(page))
2922                                 goto next;
2923
2924                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2925                                 goto next;
2926
2927                         total++;
2928                         lock_page(page);
2929                         if (!split_huge_page(page))
2930                                 split++;
2931                         unlock_page(page);
2932 next:
2933                         put_page(page);
2934                 }
2935         }
2936
2937         pr_info("%lu of %lu THP split\n", split, total);
2938
2939         return 0;
2940 }
2941 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2942                 "%llu\n");
2943
2944 static int __init split_huge_pages_debugfs(void)
2945 {
2946         debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2947                             &split_huge_pages_fops);
2948         return 0;
2949 }
2950 late_initcall(split_huge_pages_debugfs);
2951 #endif
2952
2953 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2954 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2955                 struct page *page)
2956 {
2957         struct vm_area_struct *vma = pvmw->vma;
2958         struct mm_struct *mm = vma->vm_mm;
2959         unsigned long address = pvmw->address;
2960         pmd_t pmdval;
2961         swp_entry_t entry;
2962         pmd_t pmdswp;
2963
2964         if (!(pvmw->pmd && !pvmw->pte))
2965                 return;
2966
2967         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2968         pmdval = *pvmw->pmd;
2969         pmdp_invalidate(vma, address, pvmw->pmd);
2970         if (pmd_dirty(pmdval))
2971                 set_page_dirty(page);
2972         entry = make_migration_entry(page, pmd_write(pmdval));
2973         pmdswp = swp_entry_to_pmd(entry);
2974         if (pmd_soft_dirty(pmdval))
2975                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2976         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2977         page_remove_rmap(page, true);
2978         put_page(page);
2979 }
2980
2981 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2982 {
2983         struct vm_area_struct *vma = pvmw->vma;
2984         struct mm_struct *mm = vma->vm_mm;
2985         unsigned long address = pvmw->address;
2986         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2987         pmd_t pmde;
2988         swp_entry_t entry;
2989
2990         if (!(pvmw->pmd && !pvmw->pte))
2991                 return;
2992
2993         entry = pmd_to_swp_entry(*pvmw->pmd);
2994         get_page(new);
2995         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2996         if (pmd_swp_soft_dirty(*pvmw->pmd))
2997                 pmde = pmd_mksoft_dirty(pmde);
2998         if (is_write_migration_entry(entry))
2999                 pmde = maybe_pmd_mkwrite(pmde, vma);
3000
3001         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
3002         if (PageAnon(new))
3003                 page_add_anon_rmap(new, vma, mmun_start, true);
3004         else
3005                 page_add_file_rmap(new, true);
3006         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
3007         if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
3008                 mlock_vma_page(new);
3009         update_mmu_cache_pmd(vma, address, pvmw->pmd);
3010 }
3011 #endif